Semiconductor wafer fabrication involves many high-temperature steps such as phosphorus diffusion, aluminum alloying, the deposition of coatings, hydrogen passivation, front contact formation and other processes. Currently, semiconductor wafers are typically processed either in a conventional electric thermal furnace or in an infrared (IR) furnace. Electric ovens or furnaces are often expensive and slow to use and may result in distortion of a semiconductor wafer. Impurity redistribution may also occur with a conventional processing oven, since impurities may permeate the wafer from or through the hot walls of the furnace or oven.
Rapid thermal annealers are known which utilize an optical energy source to quickly raise the temperature of a semiconductor wafer. Such annealers, however, while increasing the speed of heating, may also increase non-uniform heating of the wafer being processed. Conventional optically assisted rapid thermal annealers typically produce non-uniform light energy profiles over a wafer which may create heat stress in the wafer leading to possible breakage and undesirable residual electrical characteristics. For example, uneven heating or other process variations may result in non-uniform electrical activation, defects or wafer distortion. In addition, a uniform optical flux, if it can be achieved over a wafer, will typically result in uneven wafer heating because of differing amounts of radiative heat loss across the various regions of a wafer surface.
Improved optical processing furnaces are known which utilize photonic effects to enhance thermal reactions. Known optical furnaces are, however, generally single-batch laboratory furnaces which are not suitable for high throughput or continuous operation such as is desirable in a commercial furnace. Furthermore, known optical laboratory furnaces which are designed to process single or small batches of wafers, may be operated effectively with a much higher optical energy loss rate and therefore less efficiency than is desirable in a commercial production furnace.
The embodiments disclosed herein are intended to overcome one or more of the problems discussed above. The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.